Plotters were allegedly going to storm Podgorica parliament, shoot Milo jukanovi and install a pro-Moscow party

Serbia has deported a group of Russians suspected of involvement in a takeover plot in neighbouring Montenegro, the Guardian has learned, in the latest spin in a murky sequence of events that apparently threatened the lives of two European prime ministers.

The plotters were allegedly going to dress in police uniforms to storm the Montenegrin parliament in Podgorica, shoot the “ministers “, Milo jukanovi, and install a pro-Moscow party.

The Russian fingerprints on the October plot have heightened intrigue about Moscows ambitions in a part of Europe hitherto thought to be gravitating towards the EUs orbit.

A group of 20 Serbians and Montenegrins, some of whom had opposed with Moscow-backed separatists in eastern Ukraine, were arrested in Podgorica, the Montenegrin capital. In Serbia, meanwhile, several Russian nationals suspected of coordinating the plot were caught with 120,000 and special forces uniforms.

According to the Belgrade daily, Danas, the Russians also had encryption equipment and were able to keep track of jukanovis whereabouts.

Diplomatic sources told the Guardian the Belgrade government quietly deported the Russians after the intervention of the head of the Russian security council, Nikolai Patrushev, who flew to Belgrade on 26 October in an apparent effort to contain the scandal. The countrys interior minister, Neboja Stefanovi denied the government carried out any expulsions connected to the plot.

A source close to the Belgrade government told Patrushev, a former FSB( federal security service) chief, apologised for what he characterised as a rascal operation that did not have the Kremlins sanction. In Moscow, a Security Council official told Tass that Patrushev didnt apologise to anyone, because there is nothing to apologise for.

The Serbian government was further rattled three days after Patrushevs visit when a cache of arms was procured near the home of the prime minister, Aleksandar Vui. The weapons were discovered at a junction where Vuis car would normally slow down on his way to the house.

Stefanovi said there were strong suspicions that an organised crime gang had been hired to kill Vui for 10 m, but he would not specify who was behind the alleged plot, saying further investigation would present whether people outside the region were involved.

There will be changes in the secret service, he told the public broadcaster, RTS. I believed in the skills of people who didnt show that they have these capacities, but Ill take responsibility for this.

It is unclear whether there is a connection between the alleged assassination plots against Vui and jukanovi. But the intrigue of the past month comes against a backdrop of fierce east-west competitor.

jukanovi has been instrumental in pulling his country to the verge of Nato membership an accession protocol was signed in May which has dashed Russian hopes of securing a naval foothold on the Adriatic. According to the Montenegrin press, Moscow lobbied hard in recent years for transit and upkeep facilities at the ports of Bar and Kotor.

The importance of such facilities was demonstrated late last month when the Russian carrier, the Admiral Kuznetsov and its battle group was denied refuelling in European ports along their way to support the Russian military effort in Syria.

In Serbia, Vui has been seeking a delicate balance between Nato and Russia, and the countrys armed forces have conducted military exercises with both, although far more frequently in recent years with Nato. Vui has also refused to grant diplomatic status to Russian officials staffing a Serbian-Russian humanitarian centre established in the city of Ni in 2012, infuriating Moscow.

Western officials suspect the centre of being a Trojan horse, which could expanded as a hub for intelligence and paramilitary operations in the region. Diplomatic status, they point out, would have allowed equipment to be brought in without oversight by Serbian customs.

Some analysts have suggested the operation could have been mounted as a semi-freelance one, devoting enough distance from Moscow to be plausibly deniable if was uncovered.

Both sides have an interest in playing this as a freelance, vigilante-type thing, it allows them both to save face. Whether thats actually true is unclear. Theres simply not enough proof either to support or refute it, said Vladimir Frolov, a Moscow-based analyst.

Judging from the amount of logistical and financial support they get, it looks likely they acted with at least a tacit understanding that this was sanctioned.

A few days after the would-be takeover, a former intelligence officer, Leonid Reshetnikov, who ran a hawkish research institute in Moscow, was relieved of his duties by Putin. The Russian Institute for Strategic Study has a branch office in Belgrade, and Reshetnikov “ve been given” strong backing to the anti-Nato opposition party in Montenegro.

A security analyst from the region, who did not want to be named, said his understanding from intelligence sources was that the incidents in the Balkans are likely to be links between Russian attempts to gain influence and leveraging in the Balkans in the run-up to an anticipated Hillary Clinton US presidency, which was expected to take a harder line on Russian activity in the region.

In Moscow, the Russian foreign ministry took a dim view of this Guardian report on the Balkan events.

Maria Zakharova, spokesperson for the Russian foreign ministry wrote on Facebook: The publishing in the Guardian with a link to sources went on to say that Patrushev apologised for Russian nationalists who had planned to kill the premier of Montenegro is a classic provocation aimed at spreading knowingly false information.